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    <title>Document</title>
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<script>
    let str='a.k.j.d.w';

    //按关键字分隔字符串，返回字符串数组
    let strs=str.split('.');
    console.log(strs);

    //检查是否以某字符串开头
    console.log(str.startsWith('a.'));

    //分隔字符串
    let res=str.substring(0,3);
    console.log(res);
</script>